The optimum size of a conductor for a given voltage and current can be estimated by Kelvin's law for conductor size , which states that the size is at its optimum when the annual cost of energy wasted in the resistance is equal to the annual capital charges of providing the conductor. At times of lower interest rates, Kelvin's law indicates that thicker wires are optimal; while, when metals are expensive, thinner conductors are indicated: however, power lines are designed for long-term use, so Kelvin's law has to be used in conjunction with long-term estimates of the price of copper and aluminum as well as interest rates for capital.
the big flaw in this is that solar cells are rated in a lab under PERFECT SIMULATED SUN with no clouds bird shadows or other reductions….. including dust. real life instances are rare and almost exclusively in the soutwest. in addition they are pointed directly at the simulated sun. thats why they make tracking collector array mounts. if the array is stationary, even mounted ideally, you can reduce the output by 50%. then there are the batteries. while they are called deep cycle it refers to the capability without damage…. they do not furnish full voltage but approx. HALF the rating.. appliances wont run at less than 11vdc. inverters shut down at . there are also numerous mistakes in the load estimates…… rule of thumb. DOUBLE the textbook design results for a reliable system.